From the Supreme Court Thursday came President Barack Obama’s latest evolution on gay marriage. Obama’s Solicitor General Donald Verrilli submitted an amicus brief to the court urging the justices to guarantee marriage rights to gays in the eight states that currently have civil unions, rather than pushing for those rights in every state nationwide.

When a state such as California allows committed same-sex couples to have virtually all of the rights and benefits of marriage through laws allowing civil unions or domestic partnerships, but doesn’t allow those couples to get married, it is treating the same-sex couples differently because of their sexual orientation [which] violates the Constitution’s requirement that everyone will be treated equally.

Though its language opens the door for a broader ruling, the brief remains silent on those states that don’t allow civil unions. On its face, that seems like a considerable step back from the high rhetoric of Obama’s second inaugural speech:

We, the people, declare today that the most evident of truths – that all of us are created equal – is the star that guides us still; just as it guided our forebears through Seneca Falls, and Selma, and Stonewall; just as it guided all those men and women, sung and unsung, who left footprints along this great Mall, to hear a preacher say that we cannot walk alone; to hear a King proclaim that our individual freedom is inextricably bound to the freedom of every soul on Earth.

It is now our generation’s task to carry on what those pioneers began. For our journey is not complete until our wives, our mothers, and daughters can earn a living equal to their efforts. Our journey is not complete until our gay brothers and sisters are treated like anyone else under the law – for if we are truly created equal, then surely the love we commit to one another must be equal as well.

Obama took a personal interest in the government’s position on the gay marriage case that will be argued before the court on March 26. It is a California case, so the government didn’t necessarily need to weigh in. SCOTUSblog reporter Lyle Denniston says administration sources tell him Obama was:

…involved directly in the government’s choice of whether to enter the case at all, and then in fashioning the argument that it should make. Having previously endorsed the general idea that same-sex individuals should be allowed to marry the person they love, the President was said to have felt an obligation to have his government take part in the fundamental test of marital rights that is posed by the Proposition 8 case. The President could take the opportunity to speak to the nation on the marriage question soon.

But if Obama chose to put his government behind the case on principle, what explains the narrow argument?

Obama’s public policy position on the issue has changed over time. In 1996, when he was running for Illinois State Senate, Obama returned a signed questionnaire to a gay Chicago paper saying “I favor legalizing same-sex marriages.” Here’s his advisor Dan Pfeiffer in June 2011 saying Obama wasn’t responsible for the statement. From 2004 on, when running for the U.S. Senate, Obama said his position opposing same-sex marriage was based on his religious faith. And he famously said at a press conference in late 2010 that his feelings on the issue were “evolving.”

That position has tracked the political necessities of the moment. Back in 1996, only 27% of Americans supported the right to same-sex marriage, while 68% opposed it, but when you’re running for State Senate in a reliably Democratic district, you can stake out positions that are not in line with the rest of the state, let alone the rest of the country.

In 2004, the country had changed, but not that much. A strong majority still opposed gay marriage, and the issue cost Kerry votes against George W. Bush in some key states. At the start of his presidency, Obama declared himself still opposed to gay marriage: the country remained largely opposed as well, with 40% supporting it and 56% opposing. By this year the numbers had flipped: 54% support gay marriage, according to a recent CBS News poll, and 39% oppose it.

But Thursday’s arguments are targeted at a different audience: the nine justices, one of whom, Antonin Scalia, has likened homosexuality to bestiality and polygamy. Anthony Kennedy, the sometime swing voter on the court, wrote the path breaking ruling in the 2003 case Lawrence v. Texas, overturning a prior ruling that upheld state sodomy laws. Kennedy is a tough nut to crack. He is generally conservative, but can be convinced by appeals to liberty, especially when he has some personal exposure to the issue. So it makes sense for Obama to frame the argument narrowly, whatever his personal–or political–feelings on the issue may now be.

It is worth noting, that if the U.S. has moved far, fast on this issue, it is not necessarily setting the pace anymore. The U.S. was among the earliest countries in the world to allow gay marriage in some jurisdictions in 2003, second only to the Netherlands. Since then other countries including Portugal and South Africa, have guaranteed the right nationally. At this point it’s not just Obama or the Supreme Court trying to catch up with shifting public opinion in America; it seems America is trying to catch up with vanguard countries around the world.